When one's scrotum sticks to the inner thighs due to sweating in the groin area. This situation can be nicknamed 'Batwings' because the image created by this scenario can resemble a bat and its wings. The shaft of the penis can be see as the body and the stretched scrotum to either side can be seen as the wings. Many males (and hermaphrodites) find this common occasion displeasing.

Batman: It sure is hot in this cave.
Robin: Yeah I know, I'm beginning to have batwings.
Batman: That was very unnecessary.